Apparatus and method for precision control during grading operations of a work machine

ABSTRACT

A work machine and method for grading a ground surface may include a frame, a ground-engaging attachment, an attachment coupler coupling the ground-engaging attachment to the frame, an actuator enabling movement of the ground-engaging attachment, an adjustable linkage to adjust a position of the ground-engaging attachment relative to the frame, an adjustable linkage, a sensor, and a controller. The adjustable linkage adjusts a position of the ground-engaging attachment relative to the frame. The adjustable linkage comprises of a first portion and a second portion, an enclosure encircling the second portion wherein the enclosure creates an annular chamber between the enclosure and the second portion. A sensor is coupled to the annular chamber and measures a pressure in the chamber. A controller may be configured to monitor the sensor signal, and perform one or more actions based on the sensor signal.

CROSS-REFERENCE TO RELATED APPLICATIONS FIELD OF THE DISCLOSURE

The present disclosure relates to a work machine such as a compact track loader, and a method of optimizing precision grade control during a grading operation.

BACKGROUND

Work machines with precision grade control encounter varying soil conditions and types during operation. The variability may arise from shifts in weather patterns from day-to-day operations at a worksite or grading in urban areas where surrounding materials may contribute to soil conditions. Furthermore, the work machine may encounter dynamically changing load conditions on the ground-engaging attachment coupled to the work machine because of this variability. Because of the complexity of the systems pose, therein lies an opportunity to improve work machine operation during grading.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description and accompanying drawings. This summary is not intended to identify key or essential features of the appended claims, nor is it intended to be used as an aid in determining the scope of the appended claims.

The present disclosure relates to an apparatus and method for optimizing a precision grading operation by a work machine.

According to an aspect of the present disclosure, a work machine may include a frame, a ground-engaging attachment, an attachment coupler coupling the ground-engaging attachment to the frame, an actuator, an adjustable linkage, a sensor, and a controller. The adjustable linkage adjusts a position of the ground-engaging attachment relative to the frame. The adjustable linkage comprises of a first portion and a second portion. An enclosure encircles the second portion and creates an annular chamber between the enclosure and the second portion. A sensor is coupled to the annular chamber wherein the sensor measures a pressure in the annular chamber and creates a signal based on the pressure. A controller is configured to monitor the sensor signal and perform one or more actions based on the sensor signal. The second portion of the adjustable linkage may be floating within the enclosure.

The pressure is indicative of a load on the ground-engaging attachment.

The annular chamber may be partitioned into a first annular chamber and a second annular chamber. The sensor measures a first pressure in the first annular chamber and a second pressure in the second annular chamber wherein the sensor signal is based on the pressure differential between the first pressure and the second pressure.

The annular chamber may be filled with an incompressible fluid.

The second portion of the adjustable linkage may be floating within the enclosure.

The work machine may further comprise of a ball joint coupling the ground engaging-attachment to the work machine and a lower portion of the ground-engaging attachment. The ball joint may enable the ground-engaging attachment to pivot about a point, wherein pivoting the ground-engaging attachment about the ball joint creates a proportionate force on the pitch link

Actuation of the actuator may move the ground-engaging attachment in a direction of pitch, roll, or jaw.

The actions may comprise of determining a target grade and sending a command to move the ground-engaging attachment toward the target grade.

The actions may comprise of modifying one or more of an engine speed, a transmission torque, a brake pressure, and a travel speed.

The annular chamber may further comprise of an end chamber, the end chamber formed between an end wall of the second portion and a base of the enclosure.

In an alternative embodiment, the sensor may measure a stress on the annular chamber and create a sensor signal based on the stress. The sensor may be located between an end wall of the second portion and a base of the enclosure, or the end chamber.

A method of operating a work machine with a ground-engaging attachment may comprise of sensing hydraulic pressure differential by a sensor between a first annular chamber and a second annular chamber of a pitch link wherein the pitch link coupled to the work machine on a first end, and coupled to the ground-engaging attachment on a second. In a next step, the method includes sending a sensor signal based on the pressure differential wherein the sensor signal is indicative of a load on the ground-engaging attachment. The controller may then determine if the sensor is within an optimal range and perform one or more action based on the sensor signal.

The sensor may measure a hydraulic pressure differential between a first annular chamber and a second annular chamber of the pitch link.

The pitch link may be coupled to a top portion of the ground-engaging attachment wherein the ground-engaging attachment has a cutting edge on a bottom portion of the ground-engaging attachment. A ball joint may couple the ground engaging-attachment to the work machine and a lower portion of the ground-engaging attachment than the pitch link, the ball joint enabling the ground-engaging attachment to pivot about a point, wherein pivoting the ground-engaging attachment about the ball joint creates a proportionate force on the pitch link

Other features

Other features

Other features and aspects of the disclosure will become apparent by consideration of the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a work machine with a ground engaging attachment;

FIG. 2 is a detailed side view of the ground engagement attachment coupled to fore portion of the work machine shown as a compact track loader;

FIG. 3 is a perspective view of the adjustable linkage according to one embodiment;

FIG. 4 a is a cross-sectional view of the adjustable linkage according to the embodiment shown in FIG. 3 in a first position;

FIG. 4 b is a cross-sectional view of the adjustable linkage according to the embodiment shown in FIG. 3 in a second position;

FIG. 4 c is a cross-sectional view of the adjustable linkage according to a second embodiment in a second position; and

FIG. 5 is a method of operating a work machine with a multifunctional adjustable linkage; and

Before any embodiments are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

As used herein, unless otherwise limited or modified, lists with elements that are separated by conjunctive terms (e.g., “and”) and that are also preceded by the phrase “one or more of” or “at least one of” indicate configurations or arrangements that potentially include individual elements of the list, or any combination thereof. For example, “at least one of A, B, and C” or “one or more of A, B, and C” indicates the possibilities of only A, only B, only C, or any combination of two or more of A, B, and C (e.g., A and B; B and C; A and C; or A, B, and C).

As used herein, the term “controller” is a computing device including a processor and a memory. The “controller” may be a single device or alternatively multiple devices. The controller may further refer to any hardware, software, firmware, electronic control component, processing logic, processing device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

The term “processor” is described and shown as a single processor. However, two or more processors can be used according to particular needs, desires, or particular implementations of the controller and the described functionality. The processor may be a component of the controller, a portion of the object detector, or alternatively a part of another device. Generally, the processor can execute instructions and can manipulate data to perform the operations of the controller, including operations using algorithms, methods, functions, processes, flows, and procedures as described in the present disclosure.

FIG. 1 illustrates a work machine 100 having a frame 105. The work machine 100 is illustrated as a compact track loader. Other types of work vehicles contemplated by this disclosure include skid steers and crawler dozers, for example. A ground-engaging mechanism 110 is coupled to the frame 105 and configured to support the frame 105 above a ground surface 115. The illustrated ground-engaging mechanism 110 are illustrated as tracks but may also be wheels, for example.

The work machine 100 comprises a boom assembly 120 coupled to the frame 105. A ground-engaging attachment 125, or work tool, may be pivotally coupled at a forward portion 130 of the boom assembly 120, while a rear portion 140 of the boom assembly 125 is pivotally coupled to the frame 105. The ground-engaging attachment 125 is illustrated as a blade but may be any number of work tools such as dozer blades, box blades, soil conditioners, just to name a few possibilities. The ground-engaging attachment 125 may be coupled to the boom assembly 120 through an attachment coupler 145 such as Deere and Company's Quik-Tatch, which is an industry standard configuration and a coupler universally applicable to many Deere attachments and several after-market attachments. The attachment coupler 145 may be coupled to a forward portion 130 of the boom arms 150, or more specifically a portion of the boom arms in the fore portion of the boom assembly 120.

The boom assembly 120 is moveable relative to the frame 105 by a pair of first hydraulic cylinders 160, wherein the pair of first hydraulic cylinders 160 may also conventionally be referred to as a pair of lift cylinders (one coupled to each boom arm) for a compact track loader for movement in the direction of lift 162. The attachment coupler 145 is moveable relative to the frame 110 by a pair of second hydraulic cylinders 165, conventionally referred to as tilt cylinders, for movement in the direction of pitch 180. The movement of the ground-engaging attachment 110 (shown here as a blade) relative to the frame 105 may be referred to as roll 170 or the roll direction, pitch 180 or the pitch direction, and yaw 190 or the yaw direction.

Now referring to FIG. 2 , an exemplary embodiment of an adjustable linkage 200 coupled to a ground-engaging attachment 125 and attachment coupler 145 is shown. The adjustable linkage 200 advantageously functions as a bifunctional pitch link (hereinafter interchangeably referred to as pitch link) by enabling adjustment of the ground-engaging attachment 125 in the direction of pitch 180 and as a pressure feedback mechanism indicative of loads 210 (shown by the arrows) encountered by the ground-engaging attachment 125 during operation of the work machine 100. The load 210 correlates to the pile load encountered during the grading process. However, it is contemplated that a similar adjustable linkage with a feedback mechanism may function in a direction of lift 160, a direction of roll 170, or a direction of yaw 190. The orientation of the adjustable linkage 200 relative to the ground-engaging attachment 125 and frame 105 will determine it's functionality. The adjustable linkage 200 in the embodiment shown is coupled a top portion of the blade 125 (or ground-engaging attachment) at a first pivot coupling 215 wherein the first pivot 215 is preferably a ball joint. The adjustable linkage 200 may be coupled to the attachment coupler 145 with a joint bearing. The blade is coupled to the attachment coupler 145 at a second pivot coupling 220 wherein the second pivot coupling 220 is preferably a ball joint. As shown, the adjustable linkage and pitch actuation system can vary such that movement of the blade may be controlled in a different manner. For example, the blade actuation system may include a single pitch cylinder, which can be extended or retracted to pitch the upper portion of the blade forward or afterward. Stated differently, the position of the adjustable linkage can be controlled to adjust the blade pitch angle of the blade. Alternatively, a non-hydraulic, manual mechanism may also be provided for adjusting blade pitch in certain embodiments.

Now also referring to FIGS. 3, 4 a and 4 b, the adjustable linkage 200 adjusts the position of the ground-engaging attachment 125 with respect to the attachment coupler 145. The adjustable linkage 200, or pitch link, further comprises a first portion 225 and a second portion 230. The first portion 225 enables adjustment of the position of the blade 110, and the second portion 230 enables measurement of the load 210 on the blade. An enclosure 240 encircles the second portion 230. The enclosure 240 creates one or more annular chambers 245 between the second portion 230 and the enclosure 240. The annular chambers 245 may encircle some of the second portion 230 or a form a ring around the second portion 230. One or more sensors 250 are coupled to the annular chamber(s) 245 wherein the sensor 250 measures the chamber pressure and creates a sensor signal 255 based on the pressure. The controller 260 of the work machine 100 is then configured to monitor the sensor signal 255 and perform one or more actions based on the sensor signal 255. The first portion 225 comprise a threaded side 227 of a shaft 226 and a second side 228 with a rod-like portion of shaft 226 for connecting with the first pivot coupling 215. A nut member 265 comprises an internal thread for coupling with the threaded shaft 226. The pitch angle 270 of the ground-engaging attachment 125 may be adjusted by adjusting the length of the adjustable linkage 200 by rotating the nut member 265. Rotation of the nut member 265 advances the shaft 226 along the shaft axis 229 either in or out of the second portion 230 of the adjustable linkage 200 (described in more detail below).

In one embodiment, the second portion 230 comprises an intermediate hollow cylinder 275 and couples to the length adjusting nut member 265 through a threaded inner surface. As the length adjusting nut member 265 is rotated, the shaft 226 slides into or out of the intermediate hollow cylinder 275 along the shaft axis 229. The intermediate hollow cylinder 275 is encircled by an enclosure 240 forming an annular chamber (245 a, 245 b) therebetween. The enclosure 240 has a collar 285 to position the enclosure 240 around the external surface of the intermediate hollow cylinder 275. A closing cap 290 secures the enclosure 240 in place thereby sealing the annular chamber 245. This collar 285 is formed of a radial wall and an axial wall. The closing cap 290 closes the enclosure 240 and seals an annular gap 245 with the radial wall.

As the intermediate hollow cylinder 275 is coupled to the nut member 265, a flange 268 on the nut member 265 allows movement about shaft axis 229 while limiting linear motion of the intermediate hollow cylinder 275 relative to the enclosure 240, and thereby limiting a change in volume of the annular chamber 245 as the flange 268 abuts the collar 285.

The enclosure 240 has a base 295 rigidly coupled to the link head end 297. The link head end 297 couples the adjustable linkage 200 with the attachment coupler 145. In an alternative embodiment (not shown), the head end 297 may be coupled with the ground-engaging attachment 125 at the first pivotal coupling 215, and the shaft 226 may be coupled to the attachment coupler 145.

The annular chamber 245 may be divided into a first annular chamber 245 a, a second annular chamber 245 b and an end chamber 246 by means of seals 320 a, 320 b and 320 c. The seals 320 a and 320 b may be an integrated component of the intermediate hollow cylinder 275 and the seal 320 c may be integral to the enclosure. The first annular chamber 245 a is formed between the seals 320 a and 320 b, the second annular chamber 245 b is formed between the seals 320 b and 320 c. Seal 320 c separates the second annular chamber 245 b from end chamber 246. In a preferred embodiment, the first annular chamber 245 a and the second annular chamber 245 b are filled with an incompressible fluid 298. Ports 257 enable a refilling of fluid 298 for maintenance, if needed. An exemplary fluid is a standard hydraulic oil used in construction machinery such as skid steer machines. The end chamber 246 is formed between the end wall of the intermediate hollow cylinder and the base of the enclosure 240. In a first embodiment, the end chamber is empty and serves to collect any leakage of the fluid through the seals. A drain plug 300 at the base 295 of the enclosure 240 allows periodic cleaning of the incompressible fluid within annular chambers 245.

A sensor 250 is coupled to the enclosure 240 to measure the fluidic pressure within the enclosure 240. The sensor 250 may be configured to generate a sensor signal 255 based on the fluid pressure within the annular chamber 245. By way of a non-limiting example, a first sensor 250 a and a second sensor 250 b are provided to measure the fluid pressure within the first annular chamber 245 a and the second annular chamber 245 b, respectively. The first sensor 250 a generates a first sensor signal 255 a based on the fluid pressure in the first annular chamber 245 a. The second sensor 250 b generates a second sensor signal 255 b based on the fluid pressure in the second annular chamber 245 b. The sensor signal 255 may be based on the pressure differential between the first pressure and the second pressure. The pressure of each of the annular chambers (245 a, 245 b) may change during operation of the work machine 100 wherein the load imposed on the blade can be derived from the pressure measured by sensors (250 a, 250 b). In an alternative embodiment the pressure differential over a period of time may be gauges from the change in pressure in a single annular chamber 250.

In an alternative embodiment, the sensor may include a third sensor 245c to measure a pressure in the end chamber 246 as well if filled with incompressible fluid 298. Several combinations of pressure differentials can exist. These may include 245 a and 245c, 245 b and 245c, and 245 a, 245 b, and 245c. Alternatively, measuring a single pressure from a single chamber may also be used as an indication of fluctuations in loads encountered by the blade 125.

FIG. 2 demonstrates a simplistic model of load 210 encountered across the height of the blade 110 when engaging a homogenous pile of material. FIG. 2 also illustrates how the adjustable linkage 200 functions as a pitch link. To adjust the position of the blade 110, the length adjusting nut member 265 is rotated to adjust the length of the shaft 226 external to the intermediate hollow cylinder. If the shaft 226 is extended as shown in FIG. 4 b , it pushes the blade 215 at the first side 228 proximal to pivotal coupling 215. If the shaft 226 is retracted as shown in FIG. 4 a , it pulls the blade 215 at the at the first pivotal coupling 215.

As shown in FIG. 2 , a ball joint couples the ground-engaging attachment 125 to the attachment coupler 145 at a second location (also referred to as the second pivot coupling 220). The ball joint enables the ground-engaging attachment 125 to pivot about a point, wherein pivoting the ground-engaging attachment 125 in the direction of pitch about the ball joint creates a counter force on the adjustable linkage 200. During a grading operation, as the work machine 100 moves forward, the machine operator may control the angle of the ground engagement attachment 215 relative to the frame 105, as it engages the ground, by means of standard operator controls in directions such as yaw 190, pitch 180, roll 170, and lift. Alternatively, the work machine may function autonomously or semi-autonomously for these grading operations. As the cutting edge 128 of the dozer blade 125 cuts the earth surface, the blade 215 wants to rotate about the ball joint 195. The ball joint 195 acts as a fulcrum and the cutting force 128 creates a pull force on the adjustable linkage at the first pivot coupling 215. This pull force may be sensed by the sensor 250 as described above. Because of the linkage kinematics, the blade load variations may be measured as pressure spikes, or spikes in the pressure differential. While monitoring the pressure differential by the sensor 250 as performed by the controller 260, the controller may then automatically and precisely adjust one or more of the orientation of the blade 215 relative to the frame 105, and the operating parameters (e.g. engine speed, transmission torque, brake pressure, travel speed, etc.) to optimize grading operations. The controller 260 may further be configured to determine a target grade 310 and send a command to move the ground-engaging attachment 125 toward the target grade 310 and realign if changes in load require it to do so.

The adjustable linkage 200 described so far advantageously carries dual functions of adjusting the position of the blade 125 with respect to the attachment coupler 145 while measuring the pressure indicative of the load 210 on the blade 125.

The first portion of the adjustable linkage 200 namely the shaft 226, length adjusting nut member 265, the intermediate hollow cylinder 275 and the seal B act like a rigid member in the axial direction 229, the pulling force on the adjustable linkage 200 increase the pressure in the first annular chamber 245 a and the pressure in the second annular chamber 245 b changes accordingly.

FIG. 4C discloses an alternative embodiment where the load 210 on the adjustable linkage 200 is measured by means of a load sensor 242 (e.g. a strain gauge). As shown, load sensor 242 is positioned between the second portion 230 and the enclosure 240, within the end chamber 246. Alternative to measuring the pressure differentials between the annular chambers (245 a, 245 b, or 245 b), load sensor 242 senses fluctuations in stress as the first portion 225 moves linearly toward the second portion 230. The annular chambers (245 a, 245 b, or 245 b) may be empty and the seals (320 a, 320 b, and 320 c) may act as guiding members for any linear movement of the second portion 230 within the enclosure 240.

FIG. 5 discloses a method of operating a work machine 100 with a ground-engaging attachment 125, wherein the ground-engaging attachment 125 is coupled to the work machine through an adjustable linkage 200. In block 510, the first step requires sensing a load 210 on the pitch link (also referred to as an adjustable linkage) by a sensor (250 or 242). In block 520, the sensor sends the sensor signal 255 based on the load 210. The sensor signal 255 is indicative of the load 210 on the ground-engaging attachment 125 as the work machine performs a grading operation. In block 530, the controller determines if the sensor signal 255 is within an optimal range. The controller then performs one or more actions based on the sensor signal in block 540. This action may include modifying an operating parameter such as an engine speed, a transmission torque, a brake pressure, and a travel speed as shown in step 550. Alternatively, the controller may determine a target grade and send a command signal to move the ground-engaging attachment toward the target grade as shown in step 560. By continually or intermittently monitoring the load 210 on a blade during a grading operation, the blade pitch angle may be optimized. This method advantageously improves efficiency of the work machine, from the standpoint of productivity, fuel consumption, to name a few. As a further benefit, this may ease the mental burden placed on the work machine operator in a high workload environment when operating the work machine as the feedback provided to respond to load changes occur in real-time. 

What is claimed is:
 1. A work machine comprising: a frame; a ground-engaging attachment; an attachment coupler coupling the ground-engaging attachment to the frame; an actuator enabling movement of the ground-engaging attachment; an adjustable linkage to adjust a position of the ground-engaging attachment relative to the frame, adjustable linkage comprising a first portion and a second portion, an enclosure encircling the second portion, the enclosure creating an annular chamber between the enclosure and the second portion; a sensor coupled to the annular chamber, the sensor measuring a pressure in the annular chamber and creating a sensor signal based on the pressure; and a controller configured to monitor the sensor signal; perform one or more actions based on the sensor signal.
 2. The work machine of claim 1 wherein the pressure is indicative of a load on the ground-engaging attachment.
 3. The work machine of claim 1 wherein the annular chamber is partitioned into a first annular chamber and a second annular chamber, the sensor measuring a first pressure in the first annular chamber and a second pressure in the second annular chamber, wherein the sensor signal is based on a pressure differential between the first pressure and the second pressure.
 4. The work machine of claim 1 wherein the annular chamber is filled with an incompressible fluid.
 5. The work machine of claim 1 wherein the second portion of the adjustable linkage is floating within the enclosure.
 6. The work machine of claim 1 further comprising: a ball joint coupling the ground-engaging attachment to the attachment coupler at a second location, the ball joint enabling the ground-engaging attachment to pivot about a point, wherein pivoting the ground-engaging attachment about the ball joint creates a proportionate force on the adjustable linkage.
 7. The work machine of claim 1 wherein actuation of the actuator moves the ground-engaging attachment in a direction of pitch.
 8. The work machine of claim 1 wherein actuation of the actuator moves the ground-engaging attachment in a direction of roll and yaw.
 9. The work machine of claim 1 wherein the actions comprise of determining a target grade and sending a command to move the ground-engaging attachment toward the target grade.
 10. The work machine of claim 1 wherein the actions comprise of modifying one or more of an engine speed, a transmission torque, a brake pressure, and a travel speed.
 11. The work machine of claim 1 wherein the annular chamber comprises of an end chamber, the end chamber formed between an end wall of the second portion and a base of the enclosure.
 12. An adjustable linkage for a work machine coupled to a ground-engaging attachment, the adjustable linkage comprising: a frame; a ground-engaging attachment; an attachment coupler coupling the ground-engaging attachment to the frame; an actuator enabling movement of the ground-engaging attachment; an adjustable linkage to adjust a position of the ground-engaging attachment with respect to the attachment coupler, adjustable linkage comprising a first portion and a second portion, an enclosure encircling the second portion, the enclosure creating an annular chamber between the enclosure and the second portion; a sensor coupled to the annular chamber, the sensor measuring a stress on the annular chamber and creating a sensor signal based on the stress; a ball joint coupling the ground engaging-attachment to the attachment coupler at a second location, the ball joint enabling the ground-engaging attachment to pivot about a point, wherein pivoting the ground-engaging attachment about the ball joint creates a proportionate force on the adjustable linkage; and a controller configured to monitor the sensor signal, and modifying one or more of an engine speed, a transmission torque, a brake pressure, and a travel speed if the sensor signal is outside an optimal range.
 13. The adjustable linkage of claim 12, wherein the annular chamber comprises of an end chamber, the end chamber formed between an end wall of the second portion and a base of the enclosure, and the sensor located within the end chamber.
 14. A method of operating a work machine with a ground-engaging attachment, the method comprising: sensing a load on a pitch link by a sensor, the pitch link coupled to the work machine on a first end, and coupled to the ground-engaging attachment on a second end; sending a sensor signal based on the load, the sensor signal indicative of a load on the ground-engaging attachment; determining if the sensor signal is within an optimal range; and performing one or more actions based on the sensor signal.
 15. The method of claim 14 wherein the sensor measures a hydraulic pressure differential between a first annular chamber and a second annular chamber of the pitch link.
 16. The method of claim 14 wherein the pitch link is coupled to a top portion of the ground-engaging attachment, the ground-engaging attachment having a cutting edge on a bottom portion of the ground-engaging attachment, and a ball joint couples the ground engaging-attachment to the work machine and a lower portion of the ground-engaging attachment, the ball joint enabling the ground-engaging attachment to pivot about a point, wherein pivoting the ground-engaging attachment about the ball joint creates a proportionate force on the pitch link.
 17. The method of claim 14 wherein the actions comprise of determining a target grade and sending a command signal to move the ground-engaging attachment toward the target grade
 18. The method of claim 14 wherein actions comprise of modifying one or more of an engine speed, a transmission torque, a brake pressure, and a travel speed.
 19. The method of claim 14 wherein the sensor measures a stress on an end chamber of the annular chamber, the end chamber formed between an end wall of the second portion and a base of the enclosure, with the sensor located within the end chamber.
 20. The work machine of claim 1 wherein actuation of the actuator moves the ground-engaging attachment in a direction of pitch. 